Endometriosis is the third leading cause of gynecologic hospitalization in the United States, and affecting an estimated 14 million women in Europe. Widely used numbers for the incidence of endometriosis include 5-10% of all reproductive age women and 30-40% of all women with an infertility problem. It is a disease characterized by the presence outside the uterine cavity of tissue which is histologically identical to endometrium, i.e. the membrane lining the inside of the mammalian uterus. This misplaced tissue develops into growths or lesions (also called implants or nodules) which respond to the menstrual cycle in the same way that the endometrial tissue of the uterus does: each month the tissue builds up, breaks down, and sheds. While menstrual blood flows out from the uterus, instead the blood and tissue shed from endometrial growths has no way of flowing out. This results in internal bleeding, breakdown of blood vessels and tissue from the lesions, and a consequent chronic inflammation.
The two most common symptoms of endometriosis are pain and infertility. Symptoms can include: dysmenorrhea, i.e. pain before or after menstrual periods, as well as pain during or after sex; pelvic chronic pain or lower back, intestinal, pain; heavy menstrual periods, or spotting and bleeding between periods; painful bowel movements or painful urination during menstrual periods; infertility.
The cause of endometriosis is presently not known and several theories have been proposed to give a reason to the ectopic migration and implant of endometrial cells. Recent evidences relate the occurrence of endometriosis to an altered condition of the tissue of origin itself: the eutopic endometrium. There is an increasing agreement within the art that uncontrolled migration, implant and growth of endometriomas originate from disorders in the eutopic endometrial cells. There is currently no cure for endometriosis. A variety of treatment options exist, and there are ways to minimize the symptoms caused by the condition. Besides the use of analgesics for treating pain, treatment of endometriosis is mainly related to the suppression of ovary function in estrogens secretion, therefore hormone treatments of various entities, up to the induction of menopause in the most severe cases. Surgery is used to remove endometriomas, adhesions, peritoneal implants and deep lesions located in the recto-vaginal septum or in other sites (i.e., bladder, bowel), and to relieve pain. However, recurrences occur after both medical and surgical treatments. Young women with endometriosis are often faced with difficult decisions regarding their future reproduction. Hormone treatment, being intended for the suppression of ovary function, is not compatible with pregnancy.
N-acetyl-L-cysteine (hereinafter referred to as NAC) is a well-known drug, which has been used mainly as a mucolytic agent and in the treatment of paracetamol poisoning. In recent years it has also been acknowledged as having other beneficial properties, such as being antiinflammatory and anti-proliferative, and has been suggested for the treatment of a variety of different disorders and symptoms such as schizophrenia, diabetes and cancer. In previous studies investigating the molecular mechanisms underlying and relating to endometriosis it has been proposed that the increased cell proliferation rates in endometriosis may be induced by oxidative stress in the endometriotic tissue, caused by free radicals or ROSs. It has thus been proposed that new therapeutic strategies for endometriosis may be based on antioxidants and ROS scavengers such as NAC.